Slightly similar to my previous bug report here: viewtopic.php?&t=34297, when moving through the folder icons list with the arrow keys, a video will not preview if it is at the "beginning" of a row of files. This is probably another hard to explain bug, so I've included some screenshots that show the issue. One notable exception is that the bug does not seem to happen if the file after the selected video is also a video.

I say "beginning" because the bug happens when going forward and when going backward.
If you consider the file list as a set of rows and columns of files, when I'm moving right and I get to the last file in a row, the next file is in the first column of the next row. If that file is a video/audio file, and the file following is not a video/audio file, then the file following is previewed instead of the video/audio file.
In the same manner, when I'm moving left, and I get to the first file in a row, the next file is in the last column of the previous row. If that file is a video/audio file, and the file following is not a video/audio file, then the file following is previewed instead of the video/audio file.

I have reproduced the bug with audio files as well, and updated this post to reflect.

I'm not sure what you mean by "visible items". If you mean with a "Filter by" applied (so if I'm Filtering by video) does it happen? No, that doesn't cause the bug to happen